boards/models/post/sync.py

import xml.etree.ElementTree as et

from boards.models.attachment.downloaders import download
from boards.utils import get_file_mimetype, get_file_hash
from django.db import transaction
from boards.models import KeyPair, GlobalId, Signature, Post, Tag

EXCEPTION_NODE = 'Sync node returned an error: {}.'
EXCEPTION_OP = 'Load the OP first.'
EXCEPTION_DOWNLOAD = 'File was not downloaded.'
EXCEPTION_HASH = 'File hash does not match attachment hash.'
EXCEPTION_SIGNATURE = 'Invalid model signature for {}.'
EXCEPTION_AUTHOR_SIGNATURE = 'Model {} has no author signature.'
ENCODING_UNICODE = 'unicode'

TAG_MODEL = 'model'
TAG_REQUEST = 'request'
TAG_RESPONSE = 'response'
TAG_ID = 'id'
TAG_STATUS = 'status'
TAG_MODELS = 'models'
TAG_TITLE = 'title'
TAG_TEXT = 'text'
TAG_THREAD = 'thread'
TAG_PUB_TIME = 'pub-time'
TAG_SIGNATURES = 'signatures'
TAG_SIGNATURE = 'signature'
TAG_CONTENT = 'content'
TAG_ATTACHMENTS = 'attachments'
TAG_ATTACHMENT = 'attachment'
TAG_TAGS = 'tags'
TAG_TAG = 'tag'
TAG_ATTACHMENT_REFS = 'attachment-refs'
TAG_ATTACHMENT_REF = 'attachment-ref'
TAG_TRIPCODE = 'tripcode'
TAG_VERSION = 'version'

TYPE_GET = 'get'

ATTR_VERSION = 'version'
ATTR_TYPE = 'type'
ATTR_NAME = 'name'
ATTR_VALUE = 'value'
ATTR_MIMETYPE = 'mimetype'
ATTR_KEY = 'key'
ATTR_REF = 'ref'
ATTR_URL = 'url'
ATTR_ID_TYPE = 'id-type'

ID_TYPE_MD5 = 'md5'

STATUS_SUCCESS = 'success'


class SyncException(Exception):
    pass


class SyncManager:
    @staticmethod
    def generate_response_get(model_list: list):
        response = et.Element(TAG_RESPONSE)

        status = et.SubElement(response, TAG_STATUS)
        status.text = STATUS_SUCCESS

        models = et.SubElement(response, TAG_MODELS)

        for post in model_list:
            model = et.SubElement(models, TAG_MODEL)
            model.set(ATTR_NAME, 'post')

            global_id = post.global_id

            attachments = post.attachments.all()
            if global_id.content:
                model.append(et.fromstring(global_id.content))
                if len(attachments) > 0:
                    attachment_refs = et.SubElement(model, TAG_ATTACHMENT_REFS)
                    for file in attachments:
                        SyncManager._attachment_to_xml(
                            None, attachment_refs, file.file.file,
                            file.hash, file.file.url)
            else:
                content_tag = et.SubElement(model, TAG_CONTENT)

                tag_id = et.SubElement(content_tag, TAG_ID)
                global_id.to_xml_element(tag_id)

                title = et.SubElement(content_tag, TAG_TITLE)
                title.text = post.title

                text = et.SubElement(content_tag, TAG_TEXT)
                text.text = post.get_sync_text()

                thread = post.get_thread()
                if post.is_opening():
                    tag_tags = et.SubElement(content_tag, TAG_TAGS)
                    for tag in thread.get_tags():
                        tag_tag = et.SubElement(tag_tags, TAG_TAG)
                        tag_tag.text = tag.name
                else:
                    tag_thread = et.SubElement(content_tag, TAG_THREAD)
                    thread_id = et.SubElement(tag_thread, TAG_ID)
                    thread.get_opening_post().global_id.to_xml_element(thread_id)

                pub_time = et.SubElement(content_tag, TAG_PUB_TIME)
                pub_time.text = str(post.get_pub_time_str())

                if post.tripcode:
                    tripcode = et.SubElement(content_tag, TAG_TRIPCODE)
                    tripcode.text = post.tripcode

                if len(attachments) > 0:
                    attachments_tag = et.SubElement(content_tag, TAG_ATTACHMENTS)
                    attachment_refs = et.SubElement(model, TAG_ATTACHMENT_REFS)

                    for file in attachments:
                        SyncManager._attachment_to_xml(
                            attachments_tag, attachment_refs, file.file.file,
                            file.hash, file.file.url)
                version_tag = et.SubElement(content_tag, TAG_VERSION)
                version_tag.text = str(post.version)

                global_id.content = et.tostring(content_tag, ENCODING_UNICODE)
                global_id.save()

            signatures_tag = et.SubElement(model, TAG_SIGNATURES)
            post_signatures = global_id.signature_set.all()
            if post_signatures:
                signatures = post_signatures
            else:
                key = KeyPair.objects.get(public_key=global_id.key)
                signature = Signature(
                    key_type=key.key_type,
                    key=key.public_key,
                    signature=key.sign(global_id.content),
                    global_id=global_id,
                )
                signature.save()
                signatures = [signature]
            for signature in signatures:
                signature_tag = et.SubElement(signatures_tag, TAG_SIGNATURE)
                signature_tag.set(ATTR_TYPE, signature.key_type)
                signature_tag.set(ATTR_VALUE, signature.signature)
                signature_tag.set(ATTR_KEY, signature.key)

        return et.tostring(response, ENCODING_UNICODE)

    @staticmethod
    @transaction.atomic
    def parse_response_get(response_xml, hostname):
        tag_root = et.fromstring(response_xml)
        tag_status = tag_root.find(TAG_STATUS)
        if STATUS_SUCCESS == tag_status.text:
            tag_models = tag_root.find(TAG_MODELS)
            for tag_model in tag_models:
                tag_content = tag_model.find(TAG_CONTENT)

                content_str = et.tostring(tag_content, ENCODING_UNICODE)

                tag_id = tag_content.find(TAG_ID)
                global_id, exists = GlobalId.from_xml_element(tag_id)
                signatures = SyncManager._verify_model(global_id, content_str, tag_model)

                version = int(tag_content.find(TAG_VERSION).text)
                is_old = exists and global_id.post.version < version
                if exists and not is_old:
                    print('Post with same ID exists and is up to date.')
                else:
                    global_id.content = content_str
                    global_id.save()
                    for signature in signatures:
                        signature.global_id = global_id
                        signature.save()

                    title = tag_content.find(TAG_TITLE).text or ''
                    text = tag_content.find(TAG_TEXT).text or ''
                    pub_time = tag_content.find(TAG_PUB_TIME).text
                    tripcode_tag = tag_content.find(TAG_TRIPCODE)
                    if tripcode_tag is not None:
                        tripcode = tripcode_tag.text or ''
                    else:
                        tripcode = ''

                    thread = tag_content.find(TAG_THREAD)
                    tags = []
                    if thread:
                        thread_id = thread.find(TAG_ID)
                        op_global_id, exists = GlobalId.from_xml_element(thread_id)
                        if exists:
                            opening_post = Post.objects.get(global_id=op_global_id)
                        else:
                            raise SyncException(EXCEPTION_OP)
                    else:
                        opening_post = None
                        tag_tags = tag_content.find(TAG_TAGS)
                        for tag_tag in tag_tags:
                            tag, created = Tag.objects.get_or_create(
                                name=tag_tag.text)
                            tags.append(tag)

                    # TODO Check that the replied posts are already present
                    # before adding new ones

                    files = []
                    tag_attachments = tag_content.find(TAG_ATTACHMENTS) or list()
                    tag_refs = tag_model.find(TAG_ATTACHMENT_REFS)
                    for attachment in tag_attachments:
                        tag_ref = tag_refs.find("{}[@ref='{}']".format(
                            TAG_ATTACHMENT_REF, attachment.text))
                        url = tag_ref.get(ATTR_URL)
                        attached_file = download(hostname + url)
                        if attached_file is None:
                            raise SyncException(EXCEPTION_DOWNLOAD)

                        hash = get_file_hash(attached_file)
                        if hash != attachment.text:
                            raise SyncException(EXCEPTION_HASH)

                        files.append(attached_file)

                    if is_old:
                        post = global_id.post
                        Post.objects.update_post(
                            post, title=title, text=text, pub_time=pub_time,
                            tags=tags, files=files, tripcode=tripcode,
                            version=version)
                        print('Parsed updated post {}'.format(global_id))
                    else:
                        Post.objects.import_post(
                            title=title, text=text, pub_time=pub_time,
                            opening_post=opening_post, tags=tags,
                            global_id=global_id, files=files, tripcode=tripcode,
                            version=version)
                        print('Parsed new post {}'.format(global_id))
        else:
            raise SyncException(EXCEPTION_NODE.format(tag_status.text))

    @staticmethod
    def generate_response_list():
        response = et.Element(TAG_RESPONSE)

        status = et.SubElement(response, TAG_STATUS)
        status.text = STATUS_SUCCESS

        models = et.SubElement(response, TAG_MODELS)

        for post in Post.objects.prefetch_related('global_id').all():
            tag_model = et.SubElement(models, TAG_MODEL)
            tag_id = et.SubElement(tag_model, TAG_ID)
            post.global_id.to_xml_element(tag_id)
            tag_version = et.SubElement(tag_model, TAG_VERSION)
            tag_version.text = str(post.version)

        return et.tostring(response, ENCODING_UNICODE)

    @staticmethod
    def _verify_model(global_id, content_str, tag_model):
        """
        Verifies all signatures for a single model.
        """

        signatures = []

        tag_signatures = tag_model.find(TAG_SIGNATURES)
        has_author_signature = False
        for tag_signature in tag_signatures:
            signature_type = tag_signature.get(ATTR_TYPE)
            signature_value = tag_signature.get(ATTR_VALUE)
            signature_key = tag_signature.get(ATTR_KEY)

            if global_id.key_type == signature_type and\
                    global_id.key == signature_key:
                has_author_signature = True

            signature = Signature(key_type=signature_type,
                                  key=signature_key,
                                  signature=signature_value)

            if not KeyPair.objects.verify(signature, content_str):
                raise SyncException(EXCEPTION_SIGNATURE.format(content_str))

            signatures.append(signature)
        if not has_author_signature:
            raise SyncException(EXCEPTION_AUTHOR_SIGNATURE.format(content_str))

        return signatures

    @staticmethod
    def _attachment_to_xml(tag_attachments, tag_refs, file, hash, url):
        if tag_attachments is not None:
            mimetype = get_file_mimetype(file)
            attachment = et.SubElement(tag_attachments, TAG_ATTACHMENT)
            attachment.set(ATTR_MIMETYPE, mimetype)
            attachment.set(ATTR_ID_TYPE, ID_TYPE_MD5)
            attachment.text = hash

        attachment_ref = et.SubElement(tag_refs, TAG_ATTACHMENT_REF)
        attachment_ref.set(ATTR_REF, hash)
        attachment_ref.set(ATTR_URL, url)